How can I get a list of all the foreign key constraints I will need to remove in order to drop the table?

How do I pass a value from the HTML script tag to the Google Script File

I'm trying to transfer the following value from the index.html script tag to Code.gs

let nr = 3;
//Using the following function
google.script.run(nr);

Code.gs:

function tr(nr) {
  Logger.log(nr);
}

But when I run the function I always get the null value